1. Field of the Invention
The present invention relates to a recording control apparatus for use with a tape recorder incorporating a recording circuit. More particularly, the invention relates to a recording control apparatus allowing the tape recorder to make recordings at specific positions on a magnetic tape.
2. Description of the Prior Art
After a tape recorder records signals on a magnetic tape, it sometimes becomes necessary to replace part of the recorded signals with other signals. In such a case, the tape recorder is first placed in its reproduction mode and the tape is played back. When the desired part of the tape is reached, the recording circuit of the tape recorder is activated to record new signals where needed on the tape. After recording, the recording circuit is deactivated and the reproduction mode is again entered.
The above operations of the tape recorder are known to be performed either manually while the reproduced signals are being monitored or automatically by use of an automatic editing device.
Prior to using the conventional automatic editing device, it is necessary to record beforehand time information along the entire tape to be used. The time information has been standardized in the broadcasting industry as the time code. This is the information identifying absolute positions on the tape in its longitudinal direction. The standardized time code is a code that makes codes of the hour, minute and second, dividing the second into 30 parts, constituting a series of coded frames.
Where the tape with the time code recorded on it is to be edited by the conventional automatic editing device, the positions at which to start and end editing are first set on the device. After editing is started, the device reaches the editing start position. At that point, the device activates the recording circuit of the tape recorder to make recordings. When the editing end position is reached, the automatic editing device deactivates the recording circuit of the tape recorder.
FIG. 1 shows a typical prior art system that edits magnetic tapes based on the time code recorded thereon. This system, disclosed in Japanese Patent Laid-Open No. 58-224483, comprises a time code reading means 27 to read the time code from a tape 21, an editing time storing means 28, a recording circuit 25, a recording circuit control means 30, and a control means 29 to control these parts. An area 31 enclosed by a broken line constitutes a microprocessor.
In operation, as depicted in FIG. 2, the above system first sets and stores an editing time T.sub.1. The system then reads a time code T.sub.2 from the tape 21. The times T.sub.1 and T.sub.2 are compared, and the recording circuit is controlled accordingly. Thereafter, a check is made to see if the editing has come to an end. These steps are executed under a control program in the microprocessor 31.
One disadvantage of the prior art automatic recording apparatus that allows the tape recorder to edit tapes automatically is the difficulty in controlling editing over very short stretches of the tape or at exact tape positions, e.g., in units of one-thirtieth of a second. This makes it difficult to carry out precise editing of tapes.
The principal cause of the above problem is that the recording control apparatus is controlled by a microprocessor and its control program. To control the recording control apparatus with the microprocessor and its control program requires the control program to monitor the current tape position and the editing start position.
Generally, however, the control program has other tasks to take care of besides controlling tape editing. This leads to other disadvantages: that the processing time is not constant per unit amount of editing and that it takes time to edit the tape. Particularly in the flowchart of FIG. 2, it takes considerable time to carry out steps (1) and (2), step (1) reading the time code T.sub.2, step (2) checking to see if the times T.sub.1 and T.sub.2 match. For this reason, when editing is conventionally controlled by the microprocessor and its control program, predetermined delays need to be provided for the positions at which to start and stop editing.